The difficulties encountered in the development of methods and compositions which continuously release pharmaceutical preparations in a uniform manner over extended periods of time are well known (see, for example, Remington's Pharmaceutical Sciences, 15th Edition (1975), pages 1618-1635).
Recent developments in the area of controlling the release of drugs are disclosed in European Patent Application 81305426.9 and European Patent Application 82300416.3 which describe methods for controlling the release of drugs by microencapsulation and containment within a biodegradable matrix, respectively.
Substitution products of 1-(amino-dihalophenyl)-2-aminoethanes and the acid addition salts thereof are disclosed in U.S. Pat. No. 3,536,712, issued Oct. 27, 1970, as useful agents for enhancing the blood circulation, and as bronchodilators, analgesics, sedatives, antipyretics, antiphlogistics and antitussives in warm-blooded animals. The preparation of other related 1-(amino-dihalophenyl)-2-aminoethanols and their derivatives are disclosed in Japanese Kokai 77 83,619 (Chemical Abstracts, 87,201061r), German Offenlegungsschrift 2,804,625 (1979), German Offlegungsschrift 2,157,040 (1973), German Offelegungsschrift 2,261,914 (1974), European Patent Application 8,715 (1980) and Netherlands Patent Application 7,303,612 (1973). These applications disclose uses selected from analgesics, broncholytic, antiinflammatory, uterine spasmolytic, .beta.-mimetic and/or .beta.-blocking activities, antispasmolytic activity on cross-striped muscle structure, for tocology, reducing blood pressure by peripheral vasodilation and mobilizing body fat, and for treating allergies.
Certain phenylethanolamine derivatives and their use for the depression of fat deposition in warmblooded animals are disclosed in U.S. Pat. No. 4,407,819. U.S. Pat. No. 4,404,222 discloses certain phenylethanolamine derivatives and their use for enhancing the growth rate of meat-producing animals and improving the efficiency of feed utilization in animals so treated. Recently, Offenlegungsschrift DE 3,306,159 A1 (European Patent Application 103830) was published describing substituted phenylethylamine derivatives which were said to be growth promoters for pigs, cows, poultry, cats, dogs, rabbits, fur animals, fish, and reptiles. The copending application for U.S. patent, Ser. No. 714,240, of Goro Asato and Terence James Bentley, filed Mar. 21, 1985, discloses certain phenylethanolamine derivatives which advantageously exhibit low .beta..sub.1 heart stimulant activity which provide improved margin of safety in their use.